Drilling tools used to penetrate underground earth formations by cutting a borehole therethrough generally utilize rotary drill bits having movable cutting elements located thereon. Generally these cutting elements comprise either milled teeth formed on the cutting head or they comprise compacts or inserts which are pressed into the cutting heads. Generally oilwell drilling bits uitlize three such cutting heads called rolling cutters. Rotation of the drilling bit by rotating the drill string moves the three rolling cutters along the bottom of the borehole in a manner to gauge and scrape the rock and earth formations by action of the cutting teeth or inserts thereagainst. Problems which are normally encountered in drilling such boreholes usually involve the hardness of the rock and the susceptibility of the drill bits to breakage and rapid wear. Most efforts in improving the drill bits have been aimed at increasing their resistance to breakage and wear by metallurgical and design techniques. One area in which little work has been done to improve cutting efficiency is in the soft plastic underground rock formations where hardness of the cutting element is not the primary concern. These certain types of rock formations, when subjected to an overbalance of hydrostatic head as opposed to normal rock pore pressure, assume a state of great plasticity and resiliency. Normally there is little difficulty in forcing the teeth or inserts of the roller bits through the plastic formation to their fullest length. Even when this is accomplished the resulting drilling rates may end up being negligible or zero. The plastic rock formations are so resilient and plastic that the deformations or indentations made by the cutting elements of the bit are immediately resealed because of the action of the hydrostatic pressure from the fluids in the well bore when the cutting stresses are removed. Thus it is nearly impossible to drill through this type of rock formation utilizing compressive stresses under an overbalanced pressure condition as described. When the overbalance situation is neutralized or alleviated, very high drilling rates can be achieved in these types of formations. The present invention discloses structure for drilling in plastic and soft formations, which structure effectively forms an extruded chip cut from the formation face and separates the chip sufficiently to provide a pressure balance between the chip and the rock face.